"And then there are those that are not inherantly religious... the ones the prefer to concentrate on the here and now. That does not make them shallow or anything. For these people, the look to themselves and those around them for fulfilment."
--um, I disagree with the structure of your theory. Since it is not imcompatible to be religious and concentrate on the here and now. I don't see alot of people I know believing something because it is "fulfilling." I observe more that they are convinced of something, and acknowledge what they are convinced of. Religion, like so many other things doesn't necessarily bring "fulfillment" even if one is as you say 'inherently' religious. Fulfillment depends on a great many things.
So, I think maybe the fault I find is in the presentation of your theory. Because it is not like a religious person cannot concentrate on the here and now. In fact I think that many religions encourage this.
Aside from that, the main premise of the theory. Perhaps, I suppose that is for someone in the Scientific field to study. Everyone's heard of the "God" gene. But I don't know how solid it is. If you look at history, it seems that very few were not believers in something 'beyond.' I think we have seen that number multiply exponetially in the recent decades. I reckon it is a choice more than anything. Weigh the evidence, come to a decision.
Just like with other "tendencies" it is just that. Not a sentence, not the end, the case is not closed. Just like someone who is prone to obesity, still has a choice of lifestyle.
It's an interesting thing to think about. But I think alot of it is informational, emotional, attitude, many factors. I say that because there is such a great gap from our ancestors and us. And I don't think that its just people inheriting a gene, or becoming more INHERENTLY inclined. There's too great a number for that to be the only cause.